Day 69 Diversification of Animals

Phylogeny and the diversification of animals

Student Assessment:

Tissue and Organ System Quiz

Animals

Animals originated more than 700 million years ago

-Our evidence for this is a fossilized hormone that is produced by sea sponges. The hormone is 710 million years old.

The first animals were sea sponges or something very similar to sea sponges

-Current evidence suggests that the first animals (sea sponges) evolved from a single celled eukaryotic organisms called choanoflagellates

Phyla Porifera (Pore bearer)

A sea sponge is barely an animal.

-The sponges cells act independently.

-The cells feed themselves

-Communication between the cells is week

-There are no organs

-No true tissue

Around 680 million years ago the first animals with true tissue evolved

Phyla Cnidaria

Cnidarians

-Sea Anemones

-Sea Jellies

-Coral

Cnidarian Characteristics

-Radial symmetry or Biradial

-Diploblastic Tissue level

-Gelatinous Mesoglea

-Nerve Net

-Cnidocytes

-Gastrovascular Cavity

What makes Cnidarians stand out is their cnidocytes

-Cnidocytes are stinging cells located on tentacles

-Cnidocytes discharge a harpoon like stinging structure called a nematocyst

Between 535 and 525 million years ago was the Cambrian period

-We refer to the Cambrian Explosion as a time when many new animals evolved in a very short time

-Out of the Cambrian Explosion we got Porifera, Cnidarians, Mullusks, Arthropods, and maybe even chordata.

-All animals share a common ancestor

-Sponges are basel animals

-Eumetazoa is a clade of animals with true tissue

-Most animal phyla belong to the clade bilateria

-Most animals are invertebrates

Invertebrate diversity

No tissue Level

-Porifera

Eumetazoa (Has True Tissue)

Diploblastic Tissue Level

-Cnidaria

Bilateria

Protostomia

Triploblastic Tissue Level

-Mollusca (93,000 species)

-Annelida (16,500 species)

-Ecdysozoa (Have hard cuticles that they molt)

-Nematoda (25,000 species)

-Arthropoda (1,000,000+ species)

-Deuterostomia (Mouth forms second)

-Hemichordata (85 species)

-Echinodermata (7,000 species)

Vertebrate Diversity

-Deuterostomia

-Chordata

Vertebrates

-Myxini (Hagfish) (30 species)

-Petromyzontida (Lampreys) (35 species)

Gnothostomes

-Chondrichthyes (Sharks, rays, chimaeras) (1,000 species)

Osteichthyans

-Actinopterygii (Ray-finned fishes) (27,000 species)

Lobe-fins

-Actinistia (Coelacanths) (1-2 species)

-Dipnoi (Lungfishes) (6 species)

Tetrapods (29,000 species)

-Amphibians

-Caecilians (No legs)

-Salamanders (retain their tail as adults)

-Frogs (lack tails as adults)

Amniotes (have amniotic eggs)

The Evolution of the amniotic egg allowed for chordate animals to spread throughout land without being dependent on water to lay their eggs

-Reptiles (including aves)

-Crocodilians (23 species)

-Turtles (307 species)

-Squamates (Snakes and lizards) (7,910 species)

Birds are endothermic reptiles

Avian characteristics

-Originated from the archosaur lineage

-Flight, feathers, lungs built for flight, hollow bones

-Endothermic

-Birds have large segments of their brain devoted to sensory information

-Complex mating systems and behavioral patterns

-Migration and navigation

Feathers are elongated scales

-Birds (10,000 species)

-Mammals

-Monotremes (Lay eggs) (5 species)

-Marsupials (Mammals with a pouch) (324 species)

-Eutherians (Placental mammals) (5,010 species)